Acrylonitrile is an important commodity chemical used mainly as monomer for the manufacture of a wide variety of polymeric materials such as polymers for acrylic fibers used, for example, in textiles, and in resins, such as ABS and SAN resins. Worldwide, acrylonitrile is produced in amounts exceeding four million metric tons per year. One method for manufacturing acrylonitrile is to oxidize propylene in the presence of ammonia using air or other source of molecular oxygen as the oxidant. Such oxidation reactions, also called ammoxidation reactions, typically use a solid-particulate heterogeneous catalyst in a fluidized catalyst bed to catalyze the ammoxidation reaction and provide the desired acrylonitrile in acceptable conversion and yield. In addition to producing acrylonitrile, such ammoxidation reactions also generally produce hydrogen cyanide and other valuable co-products.
While propylene is a desirable feedstock for such ammoxidation reactions to produce acrylonitrile, it would be desirable to be able to use a less expensive feedstock such as propane. Heterogeneous catalyst materials have been developed which can be used to convert propane to acrylonitrile using a fluid bed reactor and oxygen gas, for example, as the oxidant. However, in such reactions where propane is mixed with ammonia and air, oxygen gas, or other source of molecular oxygen, and reacted at elevated temperature in the presence of a fluidized bed of particulate catalyst, hot product gases continue to oxidize after the product gases leave the catalyst bed. Such uncontrolled oxidation downstream of the fluidized catalyst bed, also referred to as afterburning, results in a loss of valuable feed material, such as propane, which could otherwise be recycled, as well as a loss of valuable products, such as acrylonitrile. Thus, it would be desirable to have a reactor apparatus and process that can be used to reduce the amount of such uncontrolled downstream oxidation or other undesirable side reaction and the loss of products and feed materials. The present invention provides such reactor apparatus and process.